Effect of ergocristine on prolactin secretion in the male rat with pituitaries grafted beneath the kidney capsule

1979 ◽  
Vol 57 (11) ◽  
pp. 1313-1316 ◽  
Author(s):  
S. H. Shin
Keyword(s):  
Bolus Injection ◽  
Decay Curve ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Male Rat ◽  
Plasma Prolactin ◽  
Elevated Plasma ◽  
Kidney Capsule ◽  
Fourfold Increase ◽  
Single Bolus Injection

Male rats in which three pituitaries were grafted beneath the kidney capsule showed approximately a fourfold increase in circulating plasma prolactin concentration. The elevated plasma prolactin concentration did not remain at a constant level but fluctuated with time. The elevated prolactin concentration declined immediately after a single bolus injection of ergocristine (30 μg/kg). The slope of the prolactin decay curve, determined by sequential blood sampling, was parallel to a theoretical slope having a 7-min half-life. This result indicates that ergocristine blocked prolactin secretion immediately and completely as the decay curve (T1/2 = 6.5 min, confidence interval 4.5–11.3) resulting from the administration of ergocristine is the same as the endogenous prolactin decay curve (T1/2 = 7 min).

Somatostatin Inhibits prolactin secretion in the estradiol primed male rat

1981 ◽  
Vol 59 (10) ◽  
pp. 1082-1088 ◽  
Author(s):  
G. R. Cooper ◽  
S. H. Shin
Keyword(s):  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Blocking Agent ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Male Rat ◽  
Dependent Manner ◽  
Intact Male ◽  
Plasma Prl

Somatostatin inhibits not only growth hormone secretion, but also the secretion of several other hormones. The role of somatostatin in prolactin (PRL) secretion has not been clearly demonstrated. The present study was undertaken to examine the effects of somatostatin on rat PRL secretion in several different circumstances where the circulating PRL level is elevated: (1) the estradiol primed intact male rat, (2) normal and (3) estradiol primed rats pretreated with pimozide, (4) normal and (5) estradiol primed hypophysectomized male rats with adenohypophyses grafted under the kidney capsule (HAG rat). Blood samples (70 μL) were taken every 2 min via an indwelling atrial cannula from conscious, unrestrained animals. In the estradiol primed intact rats, a bolus injection of somatostatin (10, 100, and 1000 μg/kg) lowered PRL levels in a dose-dependent manner. When the PRL concentration was elevated by the administration of pimozide (3 mg/kg), a dopaminergic receptor blocking agent, somatostatin was ineffective in decreasing plasma PRL concentration but the PRL concentration was lowered by somatostatin when the rat had been primed with estradiol. Somatostatin had no effect on the normal HAG rats, but lowered the plasma PRL concentration in the estradiol primed HAG rats. Since somatostatin inhibits PRL secretion only in the estradiol primed rats, it is suggested that estradiol priming creates a new environment, presumably via new or altered receptors, which can be inhibited by somatostatin.

EARLY EFFECTS OF STILBOESTROL ON GROWTH HORMONE AND PROLACTIN SECRETION AND ON PITUITARY MITOTIC ACTIVITY IN THE MALE RAT

1973 ◽  
Vol 58 (2) ◽  
pp. 227-231 ◽  
Author(s):  
H. M. LLOYD ◽  
J. D. MEARES ◽  
JOAN JACOBI
Keyword(s):  
Growth Hormone ◽  
Mitotic Activity ◽  
Single Injection ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Male Rat ◽  
Serum Prolactin ◽  
Serum Growth Hormone ◽  
Total Period ◽  
Early Effects

SUMMARY The effects of a single injection of 1 mg diethylstilboestrol dipropionate on pituitary mitotic activity and on secretion of growth hormone and prolactin were investigated in male rats on each of the first 15 days following the single dose and then at intervals for a total period of 63 days. Mitotic activity increased to a maximum on day 4 and then gradually diminished. Serum growth hormone was moderately increased during the 2nd week and serum prolactin showed a gradual rise with a return to normal on day 63. In the pituitary gland, growth hormone concentration diminished until day 28, whereas prolactin rose quickly at first, maintained a raised level and increased further on day 43. During the first 12 days, pituitary weight was significantly correlated with serum growth hormone and prolactin concentration. During days 13–28, serum prolactin, but not growth hormone, was significantly correlated with the pituitary mitotic index.

Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat

1985 ◽  
Vol 107 (3) ◽  
pp. 325-329 ◽  
Author(s):  
H. Cohen ◽  
I. Sabbagh ◽  
P. Guillaumot ◽  
J. Bertrand
Keyword(s):  
Adult Male ◽  
Physiological Saline ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Saline Control ◽  
Plasma Prolactin ◽  
Synthesis Inhibitor ◽  
Nude Rat ◽  
Prolactin Content ◽  
Pituitary Prolactin

ABSTRACT In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor α-methyltyrosine (MT) and a dopaminergic antagonist sulpiride. Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15·6 ± 1·9 (s.e.m.)- and 5·89 ± 0·6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups. In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9·2 ± 1·8 and 3·4 ± 0·7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat. J. Endocr. (1985) 107, 325–329

Role of the adrenal cortex in chronic stress-induced inhibition of prolactin secretion in male rats

1989 ◽  
Vol 120 (2) ◽  
pp. 269-273 ◽  
Author(s):  
A. López-Calderón ◽  
C. Ariznavarreta ◽  
M. D. Calderón ◽  
J. A. F. Tresguerres ◽  
M. I. Gonzalez-Quijano
Keyword(s):  
Adrenal Cortex ◽  
Chronic Stress ◽  
Immobilization Stress ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Prolonged Release ◽  
Plasma Prolactin

ABSTRACT The response of prolactin to chronic stress in intact, adrenalectomized and adrenomedullectomized male rats was studied. Immobilization stress in intact animals induced a significant increase in plasma concentrations of prolactin after 20 and 45 min and a significant decrease when the rats were submitted to chronic restraint (6 h daily for 4 days). Five weeks after adrenomedullectomy, plasma prolactin and corticosterone responses to chronic stress were not modified. In contrast, the inhibitory effect of chronic stress on prolactin secretion was totally suppressed by adrenalectomy. When treated with dexamethasone during the 4 days of restraint, adrenalectomized stressed rats showed similar plasma concentrations of prolactin to the intact stressed rats. These data indicate that the adrenal cortex is able to play an inhibitory role on prolactin secretion during stress only through a prolonged release of glucocorticoids. Journal of Endocrinology (1989) 120, 269–273

Effect of pinealectomy and melatonin treatment during pregnancy on the sexual development of the female and male rat offspring

1995 ◽  
Vol 132 (6) ◽  
pp. 765-770 ◽  
Author(s):  
B Díaz López ◽  
MD Colmenero Urquijo ◽  
ME Díaz Rodriguez ◽  
A Arce Fraguas ◽  
A Esquifino Parras ◽  
...  
Keyword(s):  
Sexual Development ◽  
Female Offspring ◽  
The Other ◽  
Male Rats ◽  
Male Rat ◽  
Plasma Prolactin ◽  
Melatonin Treatment ◽  
Control Male ◽  
Rat Offspring ◽  
Old Rats

Díaz López B, Colmenero Urquijo MD, Díaz Rodriguez ME, Arce Fraguas A, Esquifino Parras A, Marín Fernández B, Effect of pinealectomy and melatonin treatment during pregnancy on the sexual development of the female and male rat offspring. Eur J Endocrinol 1995;132:765–70. ISSN 0804–4643 Sexual development of female and male rat offspring of control, pinealectomized (PIN-X) or melatonin (MEL 2 50 μg/100 g body wt)-treated mother rats during pregnancy was studied. Newborns were studied at the following phases of sexual development: neonate (5 days old), infantile (15 days old), juvenile (25 and 30 days old) and pubertal phase (55 days). In female offspring, MEL treatment during pregnancy significantly increased plasma luteinizing hormone (LH) in 15- and 25-day-old rats; however, at the end of the prepubertal period (30 days) the concentration of plasma LH decreased significantly as compared to control rats. This hormonal pattern was different from that observed in offspring of control and PIN-X rats, which had low LH levels at 25 days of age and higher LH levels at 30 days of age. Follicle-stimulating hormone (FSH) did not vary significantly among the three groups. Plasma prolactin levels were affected by PIN-X of the mother, showing significantly higher levels in the 5-day-old offspring than in the controls; plasma prolactin levels were also affected by MEL treatment of the mother, producing hyperprolactinemia in the 30-day-old female offspring. In male offspring, sexual development in control male rats progressed rapidly with significantly increased LH and FSH levels at 25 and 30 days compared to those measured during the neonatal and infantile periods. Pinealectomy of the mother induced the following modifications: in 5-, 15- and 30-day-old male rats, decreased LH levels were measured relative to the other two groups studied in 5- and 25-day-old rats, significantly lower FSH levels than in the control rats were recorded. However, in 5- and 15-day-old rats, significantly higher prolactin levels than in control rats were measured. Melatonin injections during pregnancy decreased FSH levels at 5, 25, 30 and 55 days as compared to the control males. Also, MEL increased LH levels in 25-day-old rats and significantly decreased prolactin levels in 15- and 55-day-old rats as compared to the other two groups. These results indicate that the mother's pineal gland and MEL treatment can act on fetal development and influence the postnatal ontogeny of the hormones involved in the neuroendocrine–reproductive axis in developing rats. The effect of MEL was apparent during pubertal stages of the offspring, while the effect of PIN-X was more apparent during the juvenile period of the young rats. Beatriz Díaz López, Dpt. Biología Funcional, Arca Fisiología, Fac, Medicina, Universidad de Oviedo, 33006-Oviedo, Spain

Effects of hyperprolactinaemia and testosterone on the release of LH-releasing hormone and the gonadotrophins in intact and castrated rats

1985 ◽  
Vol 104 (1) ◽  
pp. 35-43 ◽  
Author(s):  
A. K. Brar ◽  
A. S. McNeilly ◽  
G. Fink
Keyword(s):  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Male Rats ◽  
Pituitary Stalk ◽  
Male Rat ◽  
Female Rat ◽  
Kidney Capsule ◽  
Releasing Hormone ◽  
Gonadotrophin Secretion ◽  
Lh Releasing Hormone

ABSTRACT We have investigated the effect of hyperprolactinaemia on the secretion of LH-releasing hormone (LHRH), LH and FSH in male rats of the PVG strain which were left intact, castrated or castrated and then implanted with either a 10 or 30 mm silicone elastomer capsule containing testosterone (T10 and T30 respectively). Hyperprolactinaemia was produced by pituitary grafts under the kidney capsule. Pituitary stalk blood, for LHRH estimation, and peripheral blood, for LH, FSH and prolactin, were collected under alphaxalone anaesthesia. Pituitary stalk blood was collected during three consecutive periods of 30 min each before, during and after the application of an electrical stimulus to the median eminence (ME). Hyperprolactinaemia significantly reduced the plasma concentrations of FSH in intact rats and the post-castration increase in the plasma concentrations of both LH and FSH. Neither hyperprolactinaemia nor castration had any significant effect on the spontaneous output of LHRH, but castration alone or castration plus implantation of a T30 capsule did significantly reduce the increment in LHRH output produced by ME stimulation, an effect not seen in rats bearing pituitary grafts. The T30, but not the T10 capsules suppressed the post-castration increase in the gonadotrophins, and the inhibitory effect of testosterone was not significantly affected by hyperprolactinaemia. An incidental but important finding was that the presence of pituitary grafts under the kidney capsule reduced the anaesthetic dose of alphaxalone by 63%. These results show that (i) in the male rat the inhibitory effect of hyperprolactinaemia on gonadotrophin secretion is not due to a decrease in the spontaneous release of LHRH, (ii) in contrast to the female rat the post-castration increase in gonadotrophin secretion is not accompanied by an increase in the output of LHRH, (iii) the output of LHRH in response to ME stimulation is affected by castration and testosterone but not by hyperprolactinaemia and (iv) the anaesthetic effects of alphaxalone are potentiated by hyperprolactinaemia, and this may explain in part the potentiation of alphaxalone anaesthesia by oestrogen. J. Endocr. (1985) 104, 35–43

FAILURE OF SODIUM LOADING OR DEFICIENCY TO AFFECT PLASMA PROLACTIN IN THE MALE RAT

1977 ◽  
Vol 86 (2) ◽  
pp. 299-305 ◽  
Author(s):  
J. A. M. Mattheij
Keyword(s):  
Adult Male ◽  
Plasma Aldosterone ◽  
Male Rats ◽  
Male Rat ◽  
Sodium Balance ◽  
Plasma Prolactin ◽  
Deficient Diet ◽  
Marked Rise ◽  
Sodium Metabolism ◽  
Plasma Prl

ABSTRACT The relation between plasma prolactin (PRL) and sodium metabolism was studied in adult male rats. During the experiments attention was given to the avoidance of stress. Cannulated rats were infused with 2.5 ml 5 % NaCl over a 40 min period. Plasma PRL did not change during or up to 2 h after this infusion. Other rats were subjected to a sodium deficient diet for 3 weeks. This treatment which induced a marked rise in plasma aldosterone, did not cause a change in plasma PRL. It is concluded that PRL does not have an important role in the regulation of sodium balance.

DNA SYNTHESIS AND DEPLETION OF PROLACTIN IN THE PITUITARY GLAND OF THE MALE RAT

1978 ◽  
Vol 77 (1) ◽  
pp. 129-136 ◽  
Author(s):  
H. M. LLOYD ◽  
J. M. JACOBI ◽  
J. D. MEARES
Keyword(s):  
Growth Hormone ◽  
Dna Synthesis ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Male Rat ◽  
Serum Prolactin ◽  
Inhibitory Effects ◽  
Pituitary Prolactin

Haloperidol, bromocriptine and diethylstilboestrol dipropionate were given in various régimes to male rats to determine their effects on pituitary DNA synthesis, prolactin secretion and growth hormone secretion. Haloperidol increased serum prolactin but did not stimulate pituitary DNA synthesis or reduce pituitary prolactin concentrations. Haloperidol potentiated the effects of oestrogen on serum prolactin and on pituitary DNA synthesis; pituitary prolactin concentrations were greatly reduced, and growth hormone secretion was slightly inhibited. The inhibitory effects of bromocriptine in oestrogen-stimulated rats were demonstrated by smaller pituitary weights and decreased DNA synthesis; serum prolactin levels were lowered and pituitary prolactin concentrations were increased. Haloperidol, given to rats treated with oestrogen and bromocriptine, reversed the inhibitory effects of bromocriptine on DNA synthesis and serum prolactin; pituitary prolactin concentrations fell to well below normal. The results suggest that the haloperidol potentiation of oestrogeninduced pituitary DNA synthesis may depend upon stimulation of prolactin secretion together with reduction of intracellular prolactin levels.

Serotonin stimulates prolactin secretion in the hypophysectomized adenohypophyseal grafted rat

1983 ◽  
Vol 102 (4) ◽  
pp. 511-516 ◽  
Author(s):  
K. M. Stobie ◽  
S. H. Shin
Keyword(s):  
Prolactin Secretion ◽  
Male Rats ◽  
Normal Male ◽  
Plasma Prolactin ◽  
Site Of Action ◽  
Plasma Prl ◽  
Dose Dependent Increase ◽  
Dose Dependent

Abstract. Normal male, oestrogen (E2) primed male and hypophysectomized adenohypophyseal grafted male rats (HAG rats) were used in the experiments. Serotonin creatinine sulphate was injected as a bolus via an indwelling atrial cannula in the conscious free moving rat. Serotonin caused a dose-dependent increase in plasma prolactin (Prl) in normal (1, 3 and 10 mg/kg serotonin) and E2 primed (1 and 3 mg/kg serotonin) male rats that began immediately after injection and reached a peak within 12–15 min of injection. Oestrogen priming significantly increased the magnitude of the response to serotonin. To analyze the site of action of serotonin in the rat, serotonin (1 mg/kg) was injected into HAG rats. Serotonin increased plasma Prl in this rat preparation, indicating that serotonin acts directly on the ectopic pituitary.

ATRIAL NATRIURETIC PEPTIDE IS A PHYSIOLOGICAL INHIBITOR OF ACTH RELEASE: EVIDENCE FROM IMMUNONEUTRALIZATION IN VIVO

1991 ◽  
Vol 131 (3) ◽  
pp. R9-R12 ◽  
Author(s):  
G. Fink ◽  
R.C. Dow ◽  
D. Casley ◽  
C.I. Johnston ◽  
A.T. Lim ◽  
...  
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Plasma Concentrations ◽  
Male Rats ◽  
Male Rat ◽  
Plasma Prolactin ◽  
Acth Secretion ◽  
Acth Release ◽  
Atrial Natriuretic

ABSTRACT The brain is thought to exert a predominantly stimulatory action on ACTH secretion mediated mainly by corticotrophin-releasing factor-41 (CRF-41) and arginine vasopressin (AVP). Several data, however, also point to the existence of an ACTH-inhibiting factor. Atrial natriuretic peptide (ANP), at concentrations found in hypophysial portal blood, inhibits ACTH release in vitro. The aim of the present studies was to use ANP immunoneutralization to determine whether ANP does in fact inhibit ACTH release in vivo. Intracerebroventricular infusion (I μl/min for 30 min) of sheep anti-ANP serum into male rats anaesthetized with sodium pentobarbitone had no significant effect on jugular venous plasma concentrations of ACTH or LH but did decrease significantly the plasma concentrations of prolactin. Intravenous infusion of 0.8 ml sheep anti-ANP serum but not control (non-immune) sheep serum, through an indwelling intra-atrial cannula in conscious male rats resulted in a marked and significant increase in plasma ACTH and corticosterone concentrations. The ACTH and corticosterone response to a 30-s ether stress was not significantly potentiated in the same conscious rats infused with anti-ANP serum. Intra-atrial infusion of anti-ANP did not significantly affect plasma prolactin, LH, glucose or sodium concentrations or plasma osmolality. These results show for the first time that ANP is a potent inhibitor of ACTH secretion in the conscious male rat and that, therefore, ANP is a hypothalamic neurohormone which is likely to play an important inhibitory role in the neural control of ACTH release.

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